PROJECT SUMMARY/ABSTRACT The escalating opioid overdose epidemic is one of the most serious public health problems confronting the U.S. In 2014, a record 47,055 people died from a drug overdose in the U.S., which outnumbered deaths from motor vehicle crashes by approximately one and a half times. Heroin and misuse of prescription opioids contributed to a majority of drug overdoses in 2014. Death due to drug overdose is a significant and rising cause of mortality and morbidity in Philadelphia. In 2015, almost 700 drug overdose deaths were reported in Philadelphia ? twice as many as deaths from homicide. In response, health policy, legislation, and research funding are increasingly converging in support of the distribution of naloxone, an opioid antagonist, and community-based opioid overdose prevention programs (OPP). The success of OPP is contingent upon the willingness and effectiveness of bystanders to respond to an overdose event and administer naloxone. Emergency Response Communities (ERC) are specialized smartphone-based social networks in which members are approved carriers and/or potential users of a specific medication, such as naloxone. The ERC approach is ideally suited to support, facilitate, and encourage naloxone administration in opioid overdose emergencies, but is untested to date. The model combines GPS and IP-location tracking to identify potential opioid overdose through a smartphone application or app. Towards this end, we are proposing to utilize an ERC in the development and pilot testing of a smartphone app-based naxolone intervention (ERC-NAX) in Philadelphia. Research is needed to understand the needs and barriers in communities at high-risk for opioid overdose that will enable effective design, adaption, and implementation of an ERC-NAX app. Guided by preliminary data from study investigators, the proposed pilot project will pursue three specific aims: 1) Identify barriers and facilitators of acceptance and use of a smartphone- based ERC naloxone intervention; 2) Pilot test the implementation of ERC-NAX in an ERC consisting of 55 non-medical opioid users and 55 community members; 3) Synthesize knowledge acquired in Aims 1 and 2 to be used in a subsequent R01 study to conduct a large-scale, multi-site implementation trial. This 3-year study will provide actionable evidence regarding the viability and acceptance of an app-based naloxone intervention following the ERC model. It will be developed and tested in partnership with two community partners in Philadelphia with extensive experience in overdose prevention. This proposed intervention is significant since it leverages the growing success of OPP and will empower communities at high-risk for opioid overdose to provide rapid, secure, and effective emergency response in the event of overdose. This novel intervention, which is designed to augment emergency medical services in the rapid delivery of naloxone to overdose victims, may be effective at deescalating the epidemic of opioid overdose fatalities in Philadelphia and communities elsewhere.